Manipulating water temperatures in the Nechako River

An annual Rio Tinto project to moderate elevated water temperatures in the Nechako River during sockeye salmon migration saw positive results in 2017.

Mean daily water temperatures in the Nechako River above the Stuart River confluence did not exceed 20 C between July 20 and Aug. 20, 2017.

Kevin Dobbin, a spokesperson for Rio Tinto, says the ultimate goal of the project is to minimize the frequency of occurrences of water temperatures in excess of 20 C (between July 20 and August 20) as this might impact sockeye salmon.

This is achieved by manipulating the timing and volume of reservoir water discharged, through Skins Lake Spillway releases, into the Nechako River.

“It serves to protect the sockeye salmon while they migrate through the Nechako River to spawning grounds upstream,” he explained.

The respective maximum and minimum mean daily water temperatures recorded during the 2017 control period were 19.5 C on August 9 and 16.7 C on August 17.

Dobbin said Rio Tinto BC Works considers this project to be an integral part of their operations in British Columbia.

The project is implemented by an independent third-party consultant, who in turn directs Rio Tinto to make the appropriate changes in spillway discharge to meet the objective.

Annual data is collected, analyzed, and then reported and published as the Nechako Fisheries Conservation Program report.

The Nechako River is jointly monitored by Rio Tinto, Fisheries and Oceans Canada and the B.C. Ministry of Environment.

The Nechako Fisheries Conservation Program was formed to ensure the effective implementation of a 1987 settlement agreement between the three parties.

The agreement defined a program of measures intended to conserve Nechako River chinook and protect migrating sockeye populations.

Reports relating to project, and a historical summary report of data from 1987-2016, are available at http://www.nfcp.org.